Valve for controlling fluids

ABSTRACT

A fluid control valve having a holder body that has a receptacle containing a piezoelectric actuator unit and a hydraulic coupler module that has at least one positioning piston and at least one actuating piston that is operatively connected to the positioning piston via a hydraulic coupler and actuates a valve-closure member that cooperates with at least one valve seat and in the closed position, prevents a flow of fluid from a valve chamber to a return conduit. The positioning piston is guided in the receptacle by means of a seal.

PRIOR ART

The invention is based on a valve for controlling fluids according tothe type defined in greater detail in the preamble to claim 1.

A valve this kind is known from the prior art and is used, for example,as a control module of a fuel injection valve, in particular of a commonrail injector for a diesel internal combustion engine of a motorvehicle.

The valve, which is embodied in the form of a control module, has ahousing that serves as a holder body and contains a receptacle for apiezoelectric actuator unit and a hydraulic coupler module. Thehydraulic coupler module has a control piston, which can be actuated bythe actuator unit, and an actuating piston, which is operativelyconnected to the positioning piston via a hydraulic coupler and acts ona valve-closure member that cooperates with at least one valve seat. Inthe closed position, the valve-closure member shuts off a flow of fluidfrom a valve chamber to a return flow conduit. When the valve-closuremember is open, a pressure relief occurs in the valve chamber andtherefore in a valve control chamber, which is connected to the valvechamber and is used to actuate a valve control piston or a nozzleneedle.

The valve control chamber and the valve control piston are associatedwith a nozzle module of the injection valve, the tip of which isprovided with nozzles for injecting fuel into a combustion chamber of anengine. The valve control chamber encompasses the free end of the valvecontrol piston and is connected via a fuel supply line to ahigh-pressure connection that fills it with fuel. The position of thevalve control piston can be changed as a function of the level ofpressure that the control module sets in the valve control chamber, thusmaking it possible to control the fuel injection that occurs via theinjection valve openings leading to the combustion chamber of theengine. Thus the control module determines the position of the valvecontrol piston and therefore that of the nozzle needle. The valvechamber of the control module and the valve control chamber of thenozzle module communicate with each other via an outlet throttle.

In the known valve, the coupler module and the piezoelectric actuatorunit are bathed in fuel during operation. In the hydraulic couplermodule, this is necessary because the hydraulic coupler, which isembodied in the form of a hydraulic cushion, is disposed between thepositioning piston and the actuating piston and, during an actuation,loses hydraulic fluid or fuel due to leakage and must be refilled, whichoccurs by means of the fuel surrounding the coupler module.

The piezoelectric actuator unit includes a piezoelectric actuator thatmust not come into contact with fuel. For these reasons, the actuatorunit in the prior art had to be provided with a complex housing thatalso had to be leak tested before being mounted in the holder body.

ADVANTAGES OF THE INVENTION

The valve for controlling fluids according to the present invention,with the characteristics recited in the preamble to claim 1, in whichvalve, the positioning piston is guided in the receptacle by means of aseal, has the advantage that the hydraulic coupler module can in fact bebathed in the fluid, thus assuring a refilling of the hydraulic coupler,but the region of the receptacle in which the piezoelectric actuatorunit is disposed is sealed so that it cannot come into contact with thefluid. It is therefore no longer necessary to encapsulate the actuatorunit. The actuator unit can therefore be embodied without a metal sleeveand without a corrugated bellows or diaphragm. This also eliminates theneed for the previously required complex laser welding procedures. Inaddition, the actuator unit no longer has to be tested for heliumtightness before being installed.

It is also no longer necessary to provide an O-ring to seal electricalfeeds off from the receptacle region containing the actuator unit. Sincethe receptacle region containing the actuator unit is free of fluid, itis also unnecessary to provide a return bore in the holder body, leadingfrom this region to a return conduit for conveying the fluid back to astorage tank.

The valve according to the invention can in particular be used in aninjection valve that is a component of a common rail injection system ofa diesel internal combustion engine of a motor vehicle.

In order to fix the seal in place on the positioning piston, it can beprovided with an annular groove in which the seal is seated.

Alternatively, the seal can be fixed in place on the positioning pistonso that it is disposed between an annular collar of the positioningpiston and a positioning washer of the positioning piston and is thusfixed in the axial direction of the positioning piston.

Essentially, the seal can come in the form of any annular seal capableof absorbing the stroke of the positioning piston. The stroke of thepositioning piston is a maximum of 50 mm, for example, in an injectionvalve. For example, the seal is embodied in the form of an O-ring sealor a diaphragm or bellows seal.

In order to be able to insert the positioning piston with the sealmounted on it easily into the receptacle, the receptacle is preferablyembodied as stepped in the region of the coupler module, with a firstdiameter and a second diameter that is smaller than the first diameter,the seal being disposed in the region of the second diameter. Thenduring assembly, the seal need only slide a short distance along thewall of the receptacle, which minimizes the risk of leaks.

To further simplify assembly, the receptacle is advantageously providedwith an insertion bevel, which forms a transition between the regionwith the first diameter and the region with the second diameter; duringassembly, the seal slides along this insertion bevel toward itsinstallation position.

Other advantages and advantageous embodiments of the subject of thepresent invention can be inferred from the specification, the drawingsand the claims.

DRAWINGS

Two exemplary embodiments of the valve according to the presentinvention are depicted in a schematically simplified form in thedrawings and will be explained in greater detail in the subsequentdescription.

FIG. 1 shows an injection valve with a valve according to the presentinvention;

FIG. 2 shows an enlarged view of the region II in FIG. 1;

FIG. 3 shows a holder body of the injection valve according to FIG. 1;and

FIG. 4 shows an alternative embodiment form of a valve according to thepresent invention in a depiction that corresponds to FIG. 2.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIGS. 1 to 3 show a fuel injection valve 10 designed to be installed inan internal combustion engine, not shown in detail here, of a motorvehicle, and for use as a common rail injector preferably for injectingdiesel fuel into a combustion chamber of an engine. To this end, theessential components of the fuel injection valve 10 are a nozzle module11 and a valve control module 12.

The nozzle module 11 has a nozzle body 13 in which a so-called valvecontrol piston 14 is guided in an axially movable fashion, which piston,together with a nozzle needle 15, comprises a component that can controlan opening or nozzle 16 of the injection valve 10 leading to thecombustion chamber of the engine.

The free end of the valve control piston 14 is guided in a sleeve 17against which one end of a helical spring 18 encompassing the valvecontrol piston 14 rests, the other end of which rests against a support19 connected to the valve control piston 14.

The nozzle module 11 is connected to the valve control module 12 bymeans of a clamping nut 20; a throttle plate 21 is disposed between thenozzle module 11 and the valve control module 12. The throttle plate 21,together with the sleeve 17 and the valve control piston 14, delimits avalve control chamber 22. The pressure ratios in the valve controlchamber 22 determine the position of the valve control piston 14 and thenozzle needle 15.

A supply conduit 23 that contains a supply throttle connects the valvecontrol chamber 22 to a supply line 24 for fuel and to a high-pressureaccumulator, not shown in detail here, the so-called common rail. Thefuel supply line 24 also supplies fuel to the tip of the nozzle needle15 so that when the nozzle needle 15 unblocks the opening 16, the fuelis injected into the combustion chamber of the engine.

An outlet conduit, which is not shown in the drawing and contains anoutlet throttle, also connects the valve control chamber 22 to a valvechamber 25 to which a bypass 26 connected to the fuel supply line 24also leads, which valve chamber is associated with the valve controlmodule 12. The supply conduit 23, the outlet conduit leading to thevalve chamber 25, and the bypass 26 pass through the throttle plate 21.

The valve chamber 25 contains a valve-closure member 27 that isprestressed in the direction away from the throttle plate 21 by means ofa helical spring 28 and cooperates with a first valve seat 29 embodiedas a flat seat and a second valve seat 30 embodied as a conical seat.

The valve control module 12 also includes a holder body 31 that containsthe fuel supply line 24, a receptacle 32 for a piezoelectric actuatorunit 33, and a coupler module 34. The piezoelectric actuator unit 33 isconnected to electrical control lines 35 and is operatively connected tothe hydraulic coupler module 34 via an actuator head 36.

The hydraulic coupler module 34 has a first piston 37 embodied in theform of a positioning piston, which is operatively connected to a secondpiston 39 referred to as an actuating piston via a coupler 38 embodiedin the form of a hydraulic cushion; the actuating piston 39 has asmaller diameter than the positioning piston 37. The positioning piston37 and the actuating piston 39 are guided in a cylindrical sleeve 40that stands upright on an intermediate plate 41 and contains radialbores 42 that connect a return chamber 43 disposed downstream of thevalve seat 30 to the outside of the cylindrical sleeve 40. In the closedposition, the valve-closure member 27 prevents fluid from flowingbetween the valve chamber 25 and the return chamber 43.

As is apparent from FIG. 3, the region of the receptacle 32 containingthe coupler module 34 has a return opening 44 branching off from it,which is contained in the holder body 31 and leads to an axiallyoriented return line 45 also contained in the holder body 31, which inturn leads to a fuel tank not shown in detail here. The return chamber43 is thus connected to the return line 45 via the radial bore 42 andopenings, not shown here, in a rigid, tubular spring 47.

The positioning piston 37, which the actuator head 36 engages via asupport plate 51, is provided with an enlarged diameter in the regionadjacent to the support plate 51. In this region, the positioning piston37 has an annular groove 49 that contains an O-ring 50 serving as aseal, which rests against the wall of the receptacle 32. The region ofthe receptacle 32 containing the actuator unit 33 is therefore sealed inrelation to the region of the receptacle 32 containing the couplermodule 34. During operation of the inlet valve, the positioning piston37 executes a maximum stroke of approximately 50 mm. This stroke can becompensated for by the elasticity of the material of which the O-ring 50is made.

In addition, the positioning piston 37 is provided with a positioningwasher 46 that rests against the tubular spring 47 disposed concentricto the sleeve 40 and can adjust the volume of the hydraulic coupler 38disposed between the two pistons 37 and 39.

In the region containing the tubular spring 47, the receptacle 32 has alarger diameter than in the region containing the O-ring 50. Between theregions of different diameters, an insertion bevel 48 is provided, whichfacilitates the assembly of the coupler module 34. The O-ring 50 glidesalong this bevel into its installation position. In the assembled state,the adjusting washer 46 is disposed in the vicinity of the insertionbevel 48.

FIG. 4 shows an alternative embodiment form of a valve control module 60of an injection valve of the type shown in FIG. 1. The valve controlmodule 60 essentially corresponds to the valve control module shown inFIG. 2, but is distinguished from it by means of a control piston 61whose end oriented toward the actuator head 36 is provided with anannular collar 62 that serves to fix an O-ring 50, which seals theregion of the receptacle 32 containing the actuator unit in relation tothe region of the receptacle 32 containing the coupler module 34.

The O-ring 50 is also fixed by means of a positioning washer 63 thatserves to adjust the volume of the hydraulic coupler 38 and restsagainst the tubular spring 47. The adjusting washer 63 and the O-ring 50are disposed in the smaller diameter region of the receptacle 32.

Otherwise, the design of the valve control module 60 corresponds to thatof the valve control module according to FIG. 2.

1-7. (canceled)
 8. In a valve for controlling fluids, having a holderbody (31) including a receptacle (32) containing a piezoelectricactuator unit (33) and a hydraulic coupler module (34) that has at leastone positioning piston (37, 61) and at least one actuating piston (39)that is operatively connected to the positioning piston (37, 61) via ahydraulic coupler (38) and actuates a valve-closure member (27) thatcooperates with at least one valve seat (29, 30) and in the closedposition, prevents a flow of fluid from a valve chamber (25) to a returnconduit (45), the improvement comprising a seal (50) guiding thepositioning piston (37, 61) in the receptacle (32).
 9. The valveaccording to claim 8, wherein the positioning piston (37) comprises anannular groove (49), and wherein the seal (50) is fixed in the annulargroove (49).
 10. The valve according to claim 8, wherein the positioningpiston (61) comprises an annular collar (62) and a positioning washer(63), and wherein the seal (50) is disposed between the annular collar(62) and the positioning washer (63).
 11. The valve according to claim8, wherein the seal (50) is embodied in the form of an O-ring.
 12. Thevalve according to claim 9, wherein the seal (50) is embodied in theform of an O-ring.
 13. The valve according to claim 10, wherein the seal(50) is embodied in the form of an O-ring.
 14. The valve according toclaim 8, wherein the seal is embodied in the form of a diaphragm orbellows seal.
 15. The valve according to claim 9, wherein the seal isembodied in the form of a diaphragm or bellows seal.
 16. The valveaccording to claim 10, wherein the seal is embodied in the form of adiaphragm or bellows seal.
 17. The valve according to claim 8,characterized in that the receptacle (32) is embodied with a firstdiameter in the region of the coupler module (34) and with a seconddiameter that is smaller than the first diameter, and wherein the seal(50) is disposed in the region of the second diameter.
 18. The valveaccording to claim 9, characterized in that the receptacle (32) isembodied with a first diameter in the region of the coupler module (34)and with a second diameter that is smaller than the first diameter, andwherein the seal (50) is disposed in the region of the second diameter.19. The valve according to claim 10, characterized in that thereceptacle (32) is embodied with a first diameter in the region of thecoupler module (34) and with a second diameter that is smaller than thefirst diameter, and wherein the seal (50) is disposed in the region ofthe second diameter.
 20. The valve according to claim 11, characterizedin that the receptacle (32) is embodied with a first diameter in theregion of the coupler module (34) and with a second diameter that issmaller than the first diameter, and wherein the seal (50) is disposedin the region of the second diameter.
 21. The valve according to claim14, characterized in that the receptacle (32) is embodied with a firstdiameter in the region of the coupler module (34) and with a seconddiameter that is smaller than the first diameter, and wherein the seal(50) is disposed in the region of the second diameter.
 22. The valveaccording to claim 17, wherein an insertion bevel (48) connects the tworeceptacle regions with different diameters.
 23. The valve according toclaim 18, wherein an insertion bevel (48) connects the two receptacleregions with different diameters.
 24. The valve according to claim 19,wherein an insertion bevel (48) connects the two receptacle regions withdifferent diameters.
 25. The valve according to claim 20, wherein aninsertion bevel (48) connects the two receptacle regions with differentdiameters.
 26. The valve according to claim 21, wherein an insertionbevel (48) connects the two receptacle regions with different diameters.